ES2720579T3 - Method for providing resistance to yellowing in polyamide articles, and polyamide articles obtained from this method - Google Patents

Abstract

Use of a sulfonated reagent in a process for producing a white polyamide article, comprising at least the following steps: a. polymerization of at least one monomer to obtain a polyamide in the form of a melt, granule or powder, b. formation of the polyamide article from the melt polyamide, granule or powder, c. Optionally, conversion of the polyamide article using a texturing process, the sulfonated reagent is introduced during step a. and / or stage b. and / or step c., in order to provide resistance to phenolic yellowing to the white polyamide article obtained when in contact with plastic packaging material containing phenolic compounds.

Description

DESCRIPTION

Method for providing resistance to tamping in polyamide articles, and polyamide articles obtained from this method

Field of the Invention

The present invention relates, in general, to a method of providing resistance to yellowing in polyamide articles during storage. More specifically, the present invention describes a method for obtaining phenolic yellowing white polyamide articles, such as fibers, threads, filaments and textile articles manufactured therefrom, by adding a sulfonated reagent during polymerization and / or during the polyamide article formation from a molten polyamide, such as melt spinning and / or during the conversion of the polyamide article by texturing.

Prior art

Commercial interest in polyamides, particularly based on fibers and threads used in textile fabrics, such as underwear, sportswear, leisure clothes and sleepwear, has increased greatly due to their advantages in this field, such as Easy care properties, fast drying, high durability, abrasion resistance, balanced moisture absorption, good elasticity, lightness, comfort and softness. However, polyamide fibers typically suffer from a lack of resistance to yellowing caused during storage and transport of the textile material.

Various studies have explained the phenomenon of yellowing. According to Dorfler, C (DORFLER, C. Yellowing on polyamide: Reasons and prevention. Melliand International. September 2008, Vol. 14, No. 4 pages 248-250), storage yellowing is more precisely a phenolic yellowing, caused by the reaction of nitrogen oxides, among other air gases, with phenolic substances present in the storage and transport materials. In fact, phenolic substances are used as antioxidants in packaging materials, such as films, foams and adhesives.

Plastic packaging material, such as polyethylene, contains butylated hydroxytoluene (BHT) as an antioxidant and anti-aging preservative. This antioxidant agent (BHT) in polyethylene sheets causes the appearance of a yellow color in the polyamide article in contact with the sheet, when exposed to nitrogen oxide (NOx) gases from the surroundings of sources such as air pollution , trailer engine emissions and gas ovens. This interaction produces the compound called 2,6-di-tert-butyl-4-nitrophenol (DTNP), the main source of phenolic yellowing, according to the following steps described in Amarelamento com antioxidants. Textile Chemistry September 2005, No. 80 pages 28-35.

The terminal amino (NH2) groups of the polyamide react with the colorless DTNP by capturing the hydrogen atom of the OH group of the colorless DTNP, forming a NH3 + terminal group of polyamide. The resulting DTNP ionizes and turns yellow, thereby causing yellowing in the polyamide article.

According to Litherland, A (LITHERLAND, A and YOUNG, TC. Phenolic yellowing of textiles during storage. Part 1 - Occurrence, characterization and causes. JSDC. July / August 1983 Vol. 99, pages 201-207), yellowing Textile materials during storage is a common problem and many different chemical mechanisms may be involved, depending on the nature of the textiles, dyes, finishes, packaging materials and possible contaminants. In addition to this, the manuscript also describes that a method for preventing yellowing could be to avoid residual alkalinity in the tissue from which the garments are made.

Residual alkalinity is common in textile treatments and is due to external chemical compounds used in staining, bleaching, degreasing and finishing, but it is not related to the terminal amino groups present in the polyamide structure. Avoiding residual alkalinity is sufficient to encourage non-yellowing of textile articles, such as cotton and polyester, but does not prevent phenolic yellowing in the polyamide during storage. Even if residual alkalinity caused by external compounds is avoided, "intrinsic" phenolic yellowing is still observed due to direct contact between the polyamide and the storage material containing BHT.

In addition, the use of chemicals containing phenolic compounds during polyamide processing can also increase the propensity to phenolic yellowing in polyamide articles during storage and transportation. Examples of chemicals that are applied to the polyamide during processing and may contain phenolic compounds are antioxidants, lubricants, softening agents, spinning finishes, processing aids and additives.

This type of intrinsic phenolic yellowing of polyamide is a new challenge for the textile industry.

The most common approach to counteract this problem is to treat textile fabric and articles with salts of aryl-alkyl sulfonic acid during impregnation and depletion finishing treatments, as illustrated in US Patent Application Publication. . 2009/0249555. The disadvantages of this approach are the need for an additional processing stage, which implies a high consumption of water, energy and time, which significantly increases costs and affects the environment. A further disadvantage of this approach is the fact that the polyamide thread itself is not protected in the previous phases of the manufacturing chain, such as the formation, processing, storage and transport of the polyamide threads, before tissue formation

Another approach described in WO 2011/076085 is to add about 0.7% of dicarboxylic anhydride, such as succinic anhydride, during the extrusion phase of the polyamide fiber. However, the use of this type of reagent affects the extrusion processing conditions, because they cause a significant drop in the viscosity of the polymer, by reducing the molecular weight and releasing water molecules. In addition, special drying and vacuum conditions are required in order to improve processability. Last but not least, the above document is intended for dyeable textile articles, for which the requirements in terms of resistance to yellowing are lower than those required for white polyamide fibers. In fact, dyed polyamides are less prone to yellowing because less amino groups are generally present (when stained with acid dyes) and the color masks the yellowing.

An additional radical solution to overcome the problem of yellowing would be to replace the phenolic antioxidants used in the packaging materials with non-phenolic equivalents. However, this alternative is unlikely to happen due to the extremely high costs involved in replacing antioxidants. This solution also belongs to intermediate manufacturers, therefore, outside the control of the textile industry.

The US Patent Application Publication 2011/0196093 describes a method for polymerizing a monomer to form a polyamide having a sulfoisophthalic acid incorporated therein. This sulfoisophthalic acid is used as a stain blocking agent to increase the stain resistance of articles formed from polyamide, by improving the washing ability to remove stains from, for example, wine and coffee. The easiest removal is achieved during home wash treatments. The source of the stain here is not the presence of BHT compound in the packaging material in contact with the polyamide and, therefore, is different from phenolic yellowing. In addition, the above document is intended for dyeable textile articles, for which the requirements in terms of resistance to yellowing are lower than those required for white polyamide fibers.

US Patent 3,846,507 describes a process for producing a fiber forming polyamide having an improved basic dye receptivity and reduced acid dye receptivity by melt polymerization of sodium 3,5-benzenedicarboxylic acid sulfonate with polyamide monomers. or by melt extruding a polyamide containing this sodium 3,5-benzenedicarboxylic acid sulfonate with a virgin polyamide. The intended application is clearly dyeing threads that do not have the same specificities as white fibers as explained above.

In view of the above, there is still a need to propose a method for providing resistance to yellowing in polyamide articles, which are not intended to be dyed (white polyamide articles), for which the requirement of yellowing resistance is greater. Dyed polyamide items have almost the half of the original amino terminal groups already blocked by the acid dye, which significantly reduces the tendency to phenolic yellowing.

In fact, there is no solution to prevent phenolic yellowing due to the direct contact of the polyamide with the plastic packaging material, which contains phenolic compounds, such as butylated hydroxytoluene (BHT), before tissue formation and articles of polyamide. The only existing methods prevent yellowing from the residual alkalinity of the external compounds, but they are not applicable to the polyamide or imply additional process steps that decrease processability. The solution provided by the present invention is also cost effective and environmentally friendly, since it avoids the high consumption of water, time and energy associated with textile treatments and waste treatments normally found in the industry.

Brief Description of the Invention

In view of the foregoing, the present invention provides a method of providing resistance to phenolic yellowing in white polyamide articles in contact with plastic packaging material containing phenolic compounds, such as butylated hydroxytoluene (BHT). Said method comprises at least the following steps:

to. Polymerization of at least one monomer to obtain a polyamide in the form of a melt, granule or powder,

b. formation of the polyamide article from the melt, granule or polyamide powder, c. optionally, conversion of the polyamide article using the texturing process, where step c. and a sulfonated reagent is introduced during step a. and step c., introducing the sulfonated reagent during step a. and / or b, and / or c, in order to provide resistance to phenolic yellowing to the white polyamide article obtained when in contact with plastic packaging material containing phenolic compounds, such as butylated hydroxytoluene (BHT).

Also, the invention consists in the use of a sulfonated reagent in a process for producing a white polyamide article, comprising at least the following steps:

to. Polymerization of at least one monomer to obtain a polyamide in the form of a melt, granule or powder,

b. formation of the polyamide article from the melt, granule or polyamide powder, c. optionally, conversion of the polyamide article using the texturing process, where the sulfonated reagent is introduced during step a. and / or b. and / or c., in order to provide resistance to phenolic yellowing to the white polyamide article obtained when in contact with plastic packaging material containing phenolic compounds, such as butylated hydroxytoluene (BHT).

All preferred embodiments and definitions described below for the method can be applied directly to the previous use according to the invention.

The invention also provides a white polyamide article resistant to phenolic yellowing obtained from the above method.

Detailed description of the invention

Definitions

The term "plastic packaging material" means bags, bags, lids, protective caps, bottles, jars, barrels, labels, wrapping and filling materials, covers, boxes, cases, beakers or plastic containers, such as poly (ethylene terephthalate) (PETE), high density polyethylene (HDPE), poly (vinyl chloride) (PVC), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS) and mixtures thereof .

The term "polyamide article" refers to "polyamide fiber", which is the generic expression meaning the raw material composition of a textile article and which includes cut fibers, filaments and threads; but it also refers to any erasure or any textile composition made of polyamide fiber, especially fabrics and / or clothing. The term "polyamide article" can also refer to any granule or powder that can be used to produce extruded, injected or molded articles.

The expression "white polyamide articles" means polyamide articles that appear white to an average viewer under standardized conditions. It is understood that it meets the following requirement:

A polyamide article is commercially defined as blank by those skilled in the art if it shows a whiteness index (WI) of at least 130, as measured by the standard CIE method L * a * b * (standard CIE 15: 2004 of the "Commission Internationale de I'eclairage"). In this method, the polyamide article is evaluated using a spectrophotometer or a colorimeter, and the whiteness index (WI) is measured considering the formula: WI (D65 / 10 °) = Y 800 (0.3138-x) 1700 (0.3310-y), in which D65 refers to the type of illuminant, 10 ° refers to the observation angle and Y, x and y refer to chromaticity coordinates. Other less common methodologies can be used to evaluate the whiteness of polyamide articles, such as the methodologies of Hunter, Berger, Ganz and Stenby.

In accordance with the present invention, the whiteness of the yellowing resistant polyamide articles is at least 140, measured by the CIE methodology L * a * b *. By way of comparison, the whiteness of a raw colored polyamide article (name given to polyamide articles intended to be dyed) is commonly <90, measured by the same methodology.

In the following description, the terms fiber, thread and filament can be used interchangeably without changing the meaning of the invention.

Method and use to provide resistance to phenolic yellowing in white polyamide articles

The present invention relates to the use of a sulfonated reagent in a process for producing white polyamide articles, comprising at least the following steps:

to. Polymerization of at least one monomer to obtain a polyamide in the form of a melt, granule or powder.

b. formation of the polyamide article from the melt, granule or polyamide powder, c. optionally, conversion of the polyamide article using the texturing process, where a sulfonated reagent is introduced during step a. and / or b, and / or c, in order to provide resistance to phenolic yellowing to the white polyamide article obtained when in contact with plastic packaging material containing phenolic compounds, such as butylated hydroxytoluene (BHT).

In accordance with the invention, a phenolic compound is defined as a compound having one or more hydroxyl groups directly attached to an aromatic ring. The phenolic compounds that are contained in the plastic packaging material are, for example, one or more compounds on the list comprising phenolic acids, acetophenones, phenylacetic acids, cinnamic acids, cinnamonyl aldehydes, cinnamylic alcohols, cumaric compounds, isocumarins, chalconas, aurones, dihydrochalcone, flavannes, flavones, flavanones, flavanols, anthrocyanidins, anthocyanins, biflavonyls, benzophenones, xanthones, stilbenes, quinones, betacyanines, tannins, lignin, lignans and phlobaphenes. Preferably, the phenolic antioxidant is butylated hydroxytoluene (BHT).

In the use and method according to the invention, the white polyamide articles that come into contact with plastic packaging material containing phenolic compounds, such as butylated hydroxytoluene (BHT), are also in contact with nitrogen oxides, for example, due to air pollution, drag engine emissions and / or gas ovens.

According to the invention, the polyamide, also known as nylon, can result from two different monomers (type AABB), the most important polyamide of which is poly (hexamethylene adipamide) (polyamide 6.6 or Nylon 6.6). Of course, these polyamides can be obtained from a mixture of diacids and diamines. Thus, in the case of poly (hexamethylene adipamide), the main monomers are hexamethylene diamine and adipic acid. However, these monomers may comprise up to 25 mol% of other diamine or diacid monomers or even amino acid or lactam monomers. The polyamide according to the invention can also result from a single monomer (type AB), whose most important polyamide is polycaprolactam (or polyamide 6 or Nylon 6). Of course, these polyamides can be obtained from a mixture of lactams and / or amino acids. In the case of polycaprolactam, the main monomer is caprolactam. However, these monomers may comprise up to 25 mol% of other amino acid or lactam monomers, or even diamine or diacid monomers. More generally, the polyamide is selected from the group consisting of aliphatic, semi-aromatic and aromatic polyamides, and mixtures thereof. Advantageously, the aliphatic polyamide, which is preferred, is selected from the group consisting of polyamide 6, polyamide 6.6, polyamide 5.6, polyamide 5.10, polyamide 6.12, polyamide 11, polyamide 12, polyamide 10.10, polyamide 4.6 and mixtures thereof. Even more preferably, the polyamide is selected from the group consisting of polyamide 6, polyamide 6.6 and mixtures thereof, preferably polyamide 6.6. Two-component copolymers, blends and fibers made of polyamide and other polymers are also part of the present invention. A particularly preferred polyamide according to the present invention is a polyamide 6.6 containing 1 to 5% caprolactam.

According to the invention, the sulfonated reagent includes functional groups that are associated with the free amino terminal groups of the polyamide. Functional groups of this type belong to the group of sulfonyl groups, preferably a sulfonate functional group with the formula: R-SO3, in which the hydrocarbon R substituent may be aliphatic, aromatic or alicyclic, having one or more functional groups, such as carboxylic acids and derivatives thereof, preferably R is an aromatic substituent with one or more carboxylic acid functional groups, or R is an aryl group substituted with at least one C3 to C20 alkyl group, such as a Ce a alkyl group C16 The term "alkyl" refers to saturated linear and branched chain aliphatic hydrocarbon groups having at least one carbon atom, e.g. eg, from 1 to 18 carbon atoms.

The sulfonated reagent is advantageously selected from the group consisting of aromatic, aliphatic or sulfonated alicyclic compounds. Preferably, the sulfonated reagent is a sulfonated aromatic acid, salt, anhydride or mixture thereof. More preferably, the sulfonated reagent is selected from the group consisting of sulfoisophthalic acids, sulfobenzoic acids, sulfosalicylic acid, sulfonic acids, salts thereof, anhydrides thereof and mixtures thereof.

In one embodiment, the sulfonated reagent is a sulfoisophthalic acid salt, in particular an alkali metal salt of sulfoisophthalic acid. The alkali metal salt is selected, in this case, from the group consisting of Na, Li, K, preferably Na or Li. The best results are obtained in the preferred embodiment, wherein the reagent is selected from the group consisting of a sodium salt of 5-sulfoisophthalic acid (AlSNa), a lithium salt of 5-sulfoisophthalic acid (AlSLi) and / or mixtures thereof.

In another embodiment, the sulfonated reagent is an aryl alkyl sulfonic acid salt, wherein the alkyl and aryl groups may be optionally substituted with one or more substituents, such as halogen, CN, OH, NO2, amino, alkyl, cycloalkyl , alkenyl, alkynyl, alkoxy, aryloxy, substituted alkyloxy, alkylcarbonyl, alkylcarboxy, alkylamino or arylthio. Preferably, the sulfonated reagent is an aryl alkyl sulfonic acid salt, wherein the cationic ions include alkali metal cations and alkylammonium salts. The aryl alkyl sulfonic acid salt is most preferably N, N-bis (2-hydroxyethyl) -N-methyl- (z) -9-octadecen-1-aminium chloride compositions, benzenesulfonic acid dodecyl compound with 2-aminoethanol (1: 1); benzenesulfonic acid dodecyl compound with 2,2,2-nitrilotris (ethanol) (1: 1); mono (2-ethoylhexyl) ester of sulfuric acid, sodium salt; alkylbenzenesulfonic, triethanolamine salt; and combinations thereof.

Commercially available compositions that include aryl alkyl sulfonic acid salts are available under the trade names Depicol LG, Stabilon® CT, Ultraphor® AUC-NY, CHT-FASERSCHUTZ RPY SPEZ, Umidol APY liq, Levasalt AY and Rucolan VG1. The commercial product used in the present invention is Stabilon® CT, which is an aqueous solution of aryl alkyl sulfonic acid salts containing: 2.5-5% of -N, N-bis (2-hydroxyethyl) chloride -N-methyl- (Z) -9-octadecen-1-aminium; 20-22% benzenesulfonic acid, dodecyl compound with 2-aminoethanol (1: 1) and 20-30% benzenesulfonic acid, dodecyl compound with 2.2 ', 2 "-nitrilotris (ethanol) (1: 1).

According to the use and method of the invention, the sulfonated reagent is advantageously introduced in an amount of 0.01 to 5.0%, preferably 0.3 to 2.0% by weight of the total weight of the polyamide article .

With reference again to the method and use, the method or procedure includes a step a. of polymerization of at least one monomer to obtain a polyamide in molten form, granule or powder, a step b. of forming the polyamide article from the melt, granule or polyamide powder, and, optionally, a step c. of converting the polyamide article using the texturing process,

First embodiment: introduction during stage a.

According to a first embodiment of the present invention, the introduction of the sulfonated reagent is implemented during step a.

In this first embodiment, the sulfonated reagent can be introduced in an amount of 0.01% to 5.0% by weight of the total weight of the polyamide article, preferably 0.3 to 2.0% by weight. The sulfonated reagent can be added alone or as a standard batch. The term "standard batch" is further defined as a concentrate of the sulfonated reagent in a support. Any suitable support, a compound or a mixture of compounds known in the art, chemically and / or physically compatible with the polyamide, can be used for the preparation of the standard batch. The support is typically chosen from thermoplastic polymers, organic solvents, oils and water. The standard batch may include any ratio of the reagent to the support, more specifically from 10 to 40% by weight of the reagent in the support. In a specific embodiment of step a, the sulfonated reagent is added as a standard batch with the use of water as support.

Stage a. it may comprise any polymerization process known to those skilled in the art, including continuous polymerization and / or discontinuous polymerization. Most preferably, the method or method according to the invention is a batch polymerization.

The polymerization of at least one monomer to obtain a polyamide in the form of melt, granules or powder generally comprises the following steps:

a0. Preparation and optionally concentration by evaporation of water, of a monomer containing aqueous solution,

a1. Polymerization, under pressure, of the monomer containing aqueous solution, optionally concentrated, a2. Reduction of the pressure of the polymerization medium in order to separate the residual water by evaporation.

a3. Optional maintenance of the polymer temperature, at atmospheric pressure or under reduced pressure, in order to obtain the desired degree of polymerization.

a4. Recovery of polyamide as a melt or transformation of molten polyamide into granules or powder.

In the first stage a0. The concentration is generally carried out in an "evaporator", a device known to the person skilled in the art. This may be, for example, a static evaporator with a coil-type internal heat exchanger, an evaporator with a loop for recirculation through an external exchanger, and the like.

In the case of an AABB polyamide, the monomer-containing aqueous solution is an aqueous solution of a salt of diacid (or dicarboxylic acid) and diamine, obtained by mixing at least one diamine and a diacid, advantageously in a stoichiometric amount and in the presence of Water. In the case of polyamide 66, the aqueous solution containing monomer is a nylon salt solution obtained by mixing adipic acid, hexamethylenediamine and water. In the case of an AB polyamide, the aqueous solution containing monomer is obtained by mixing a lactam and / or an amino acid with a small amount of water. The proportion by weight of water is generally between 1 and 15%. So, water evaporation in this case is not mandatory.

In a preferred embodiment, the diacid monomer is selected from the group consisting of adipic, glutaric, subic, sebacic, dodecanedioic, 1,2- or 1,3-cyclohexanedicarboxylic acid, 1,2- or 1,3-phenylenediacetic acid, acid Isophthalic 1,2-or 1,3-cyclohexanediacetic acid, p- (tert-butyl) isophthalic acid, terephthalic acid, azelaic acid, pimelic acid, 4,4'-benzophenonadicarboxylic acid; 2,5-naphthalenedicarboxylic acid or 5-sulfoisophthalic acid or an alkaline salt thereof, and / or mixtures thereof. The preferred dicarboxylic acid is adipic acid.

In a preferred embodiment, the diamine monomer is selected from the group consisting of hexamethylenediamine, heptamethylenediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, 2-methylpentamethylenediamine, undecamethylenediamine, dodemethylamine, dodemethylamine, dodemethylamine, dodemethylamine, dodemethylamine, dodemethylamine, dodemethylamine, dodemethylamine, dodemethylamine; 2-methylhexamethylene diamine; 3-methylhexamethylene diamine; 2,5-dimethylhexamethylene diamine; 2,2-dimethylpentamethylenediamine; 5-methylnonanodiamine; 2,2,4- and 2,4,4-trimethylhexamethylene diamine; 2,2,7,7-tetramethyloctamethylene diamine; meta-xylylenediamine; para-xylylenediamine; diaminodicyclohexylmethane and C2-C16 aliphatic diamines which may be substituted with one or more alkyl groups, and / or mixtures thereof. The preferred diamine is hexamethylene diamine.

Lactam or amino acid monomers can be chosen, for example, from caprolactam, 6-aminohexanoic acid; 5-aminopentanoic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid or dodecanolactam, and mixtures thereof. The preferred lactam is caprolactam.

Then, in the second step a1., The concentrated aqueous solution is transferred to an autoclave, followed by an increase in pressure. It reaches the final concentration of the concentrated aqueous solution, typically nylon salt, and encourages the start of polymerization, under an advantageously regulated pressure between 1.5 and 2.5 MPa.

In the third stage a2., The pressure reduction consists in a decompression of the polymerization medium in order to separate the residual water by evaporation.

Then, according to step a3., The polyamide can be subsequently maintained for a predetermined time at a polymerization temperature, and at atmospheric pressure or under reduced pressure in order to obtain the desired degree of polymerization, homogeneity and viscosity. To stage a3. It is referred to as finished. Finally, in step a4., The polyamide is recovered as a melt or transformed into granules or powder. The transformation into granules is well known to the person skilled in the art. It usually consists of extruding the molten polyamide and granulating it.

Transformation into a powder is also a known technique. It generally consists of solvent dispersion, emulsion polymerization and precipitation techniques.

These phases are known to the person skilled in the art and are those used in conventional industrial processes for the manufacture of polyamide from an aqueous solution of diacid and diamine salt.

In this first embodiment, in which the sulfonated reagent is introduced during step a., It is preferred that the sulfonated reagent is introduced at the beginning of step a1., In particular that a standard batch containing the sulfonated reagent is introduced into the autoclave at the beginning of the stage. a1. of polymerization. In this way, the polyamide polymerizes in the presence of the sulfonated reagent, producing polyamide articles resistant to yellowing.

According to this first embodiment, after stage a., Stage b. The formation of the polyamide article is carried out from the melt, granule or polyamide powder obtained.

This stage b. it is described further below in the second embodiment; generally it comprises a melt spin extrusion step to first form a polyamide fiber. This polyamide fiber it can then be transformed into another polyamide article as described above, in particular a textile fabric and / or garment. The methods for transforming the polyamide fiber into a polyamide article, such as a textile fabric or garment are well known to the person skilled in the art.

Second embodiment: introduction during stage b

According to a second embodiment of the present invention, the introduction of the sulfonated reagent is implemented during step b. of forming the polyamide article from the melt, granule or polyamide powder.

Stage b. The formation of the polyamide article from the melt, granule or polyamide powder generally comprises a step of extrusion of melt spinning in order to first form a polyamide fiber. This polyamide fiber can then be transformed into another polyamide article as described above, in particular a textile fabric and / or a garment. The methods of transforming the polyamide fiber into a polyamide article, such as a textile fabric or a garment are well known to the person skilled in the art.

In this second embodiment, the sulfonated reagent can be introduced in an amount of 0.01% to 5.0% by weight of the total polyamide article, preferably 0.3 to 2.0% by weight. The sulfonated reagent can be added alone or as a standard batch. The definition of standard batch in this embodiment is the same as given above. In this particular embodiment, the sulfonated reagent is advantageously introduced as a standard batch in a polyamide support 6 or 66, preferably a polyamide support 6.

According to the invention, it is understood that the term "melt spinning" means the extrusion process of converting the polyamide into a molten form into polyamide fibers. The polyamide in the molten form may be the polyamide melt obtained directly from step a. described above or can be produced by melt extrusion of the granules or the powder obtained at the end of step a. directly or after storage and / or transport.

The polyamide obtained in step a. It can be fed to the melt spinning device in the form of granule, powder or melt. Any conventional extrusion spinning means suitable for extrusion of polyamide by melt spinning, these means being well known to a person skilled in the art, can be used to form the polyamide article from the polyamide resulting from step a ., such as single spindle extruder, double spindle extruder and rotating grid head. Extrusion by melt spinning is further defined as LOY (acronym for low orientation yarn), POY (acronym for partial orientation thread), FDY (acronym for fully stretched thread), FOY oriented), LDI (acronym for low denier industrial) or HDI (acronym for high denier industrial).

Melt spinning extrusion generally comprises the following steps:

b0. Feed the melt, granule or polyamide powder into the inlet of a screw extruder or a rotating grid head,

b1. Fusion, homogenization and pressurization of polyamide.

b2. Filament fused polyamide spinning,

b3. Cooling of the filaments.

In the first stage b0., The melt, granule or polyamide powder is added to the inlet of a spindle extruder or rotary grid head, a device known to the person skilled in the art.

Then, in the second stage b1., The polyamide melts, homogenizes and pressurizes inside the spindle extruder or rotary grid head, at a specific temperature and pressure, which is usually above the melting temperature of polyamide

Then, according to step b2., The molten polyamide is spun into filaments at a specific pressure, temperature and flow rate, with the use of a spinning extruder screen package containing filtration elements and a row.

The stage b3. it refers to the cooling of the filaments to the solidified form and to the winding of the polyamide filaments in coils.

Optionally, the extruder can be equipped with a measuring system for the introduction of additives such as standard batches in the main polymer, in step b0. and / or b1.

In this second embodiment, the sulfonated reagent is preferably introduced continuously during step b0. It can be added in the form of a powder, liquid standard batch or solid standard batch, by means of a metering pump or a gravimetric feeding apparatus. The sulfonated reagent is mixed in the molten state with the molten polyamide, before the fiber is formed. Any suitable support compatible with polyamide can be used for the preparation of the standard batch. The standard batch may include any ratio of the sulfonated reagent with respect to the support, more specifically 10 to 40% of the sulfonated reagent in the support. In this particular embodiment, the sulfonated reagent is advantageously introduced as a standard batch in a polyamide support 6 or 66, preferably a polyamide support 6.

In a particular embodiment of this second embodiment, the sulfonated reagent is advantageously added continuously to step b0. of the rotating head of the grid in the form of a liquid standard batch, by means of a metering pump. The standard batch is previously produced by mixing the support, which is preferably water, with the sulfonated reagent.

In another particular embodiment of this second embodiment, the sulfonated reagent is continuously added to step b0. of the single-screw extruder in the form of a solid standard batch, by means of a feeding apparatus. The standard batch is previously produced by mixing the support, which is preferably polyamide 6.6, using the sulfonated reagent an extrusion process by mixing. The standard batch is introduced in step b1. in a granulated form.

Third embodiment: introduction during stages a and b

According to a third embodiment of the present invention, the introduction of the sulfonated reagent is carried out both during step a. as stage b.

In this third embodiment, the total amount of sulfonated reagent introduced is from 0.01% to 5.0% by weight of the total polyamide article, preferably from 0.3 to 2.0% by weight. The sulfonated reagent can be added alone or in the form of a standard batch.

Advantageously, in stage a. 0.005 to 2.5% by weight is added and in step b. 0.005 to 2.5% by weight is also added.

Each of the introductions in each of the stages (a. And b.) Can be made according to the above description.

Fourth embodiment: introduction during stage c.

In accordance with the fourth embodiment of the present invention, the polyamide fiber is converted using the texturing process. This process comprises any technology known to those skilled in the art, such as false twist texturing, fixed false twist texturing and air jet texturing. The most preferred is false twist texturing.

The method may include the following stages:

c1 The fiber is removed from the package and passes to the delivery rollers.

c2 The fiber passes through a heater, then to a cold area.

c3 The fiber passes through a spindle that contains rotating discs (friction aggregates)

c4 Mix points and cone oil are applied to the fiber.

c5 The fiber is wound in coils.

Where there is a stretch relationship to the fiber by altering the speed ratio of c1 and c5. Where a special oil for cones is used during stage c4.

In step c1, the fiber is advantageously placed in a fillet and unwound from the coils to the delivery roller. Step c2 preferably involves passing the fiber into a heater, with a temperature of 120 ° C to 400 ° C, in order to help the mechanical action of stretching and twisting the fibers when softened (making them more malleable) . Then the fiber cools.

Stage c3 is where torsion, volume, curling and texture are generated in the fiber. The amount of torque is changed by altering the speed of the disks, the arrangement of the disks and the D / Y ratio. The D / Y ratio changes the speed ratio between the friction discs and the linear velocity of the fiber. This ratio is preferably 1.0 to 2.8. The arrangement of the disc is advantageously from 1/2/1 to 1/8/1, being a guide disk / work disk / guide disk.

According to step c4, mixing points and cone oil are applied to the fiber. The mixing improves the physical and aesthetic characteristics and it is preferable that there are at least 30 interlaced per meter. Cones oil provides lubrication. In the present invention a special oil for cones is used, which consists of a mixture of sulfonated reagent, mineral or synthetic oils and surfactants. The sulfonated reagent is present in an amount of 10 to 30% by weight, oils of 60 to 80% by weight and surfactants of 5 to 15% by weight of the total cones oil formulation. The sulfonated reagent is applied topically to the fiber as cone oil during step c4 by any method known to those skilled in the art, such as guides or greasing rollers. The cone oil may additionally comprise additional compositions, such as stabilizers, antioxidants, softeners, finishes, antistatic agents, functional additives, rheology modifiers, emulsifiers, corrosion inhibitors, anti-splashes and combinations thereof.

Stage c5. it is the winding process, in which the fiber is wound in coils; The winding speed can vary from 150 m / min to 1500 m / min.

The stretch ratio is given to the fiber by altering the speed ratio of stage c1 and stage c5, and is an important parameter of the procedure to achieve the desired linear density. The stretching ratio is advantageously from 1.10 to 4.00. Threads of more than 1 layer are possible, such as 1 to 8 layers.

Fifth embodiment: introduction during stages a and c.

In accordance with the fifth embodiment of the use and the method of the present invention, the introduction of the sulfonated reagent is carried out both during step a. as stage c.

In this fifth embodiment, the total amount of sulfonated reagent introduced is from 0.01% to 5.0% by weight of the total polyamide article, preferably from 0.3 to 2.0% by weight. The sulfonated reagent can be added on its own or in the form of a standard batch, or in the form of a cone oil.

Advantageously, in step a, 0.005 to 2.5% by weight is added and in step c. 0.005 to 2.5% by weight is also added.

Each of the introductions in each of the stages (a. And c.) Can be made in accordance with the above descriptions.

Additives may be introduced during the method of the invention. The additives are selected from: antioxidants, stabilizers, such as heat or light stabilizers, colorants, pigments, nucleating agents, such as talcum, mattifying agents, such as titanium dioxide or zinc sulphide, processing aids, biocides, modifiers of viscosity, catalysts, FIR emitting minerals, biodegradable "converting" additives, antistatic additives, functional additives, optical brightening agents, nanocapsules, antibacterial agents, anti-mites, anti-fungi or other conventional additives. These additives are generally added in step a0 and / or a1 and / or b0 and / or b3, in an amount of 0.001% to 10% by weight of the polyamide article.

The polyamide article may be any known in the art. In one embodiment, the article is a fiber (cut fiber), a thread, a filament or a deletion or a textile article made of said fiber, thread or filament. The textile article may be any textile article known in the art that includes, but is not limited to woven fabrics, knitted fabrics, nonwoven fabrics, ropes, cords, sewing threads, and so on.

These items are subsequently used in a large number of applications, particularly in carpets, rugs, upholstery, parachutes, tents, sacks, hosiery, underwear, sportswear, warm clothes, and so on.

Other details or advantages of the invention will be more clearly apparent in view of the examples given below.

Examples

A series of polyamide articles (Examples 1, 2, 3, 4, 7 and 8), a comparative polyamide article (Examples 5 and 6) and a control polyamide article (Example 9) are formed and evaluated to determine the phenolic yellowing, the content of amino terminal groups (AEG) and viscosity in solution (IVN).

Phenolic Yellowing

Knitted fabrics were produced from the different polyamide articles and submitted to the Courtalds ⁱ S ^or 105-X18: 2007 test "Evaluation of the phenolic yellowing potential of the materials". In this method, tissue samples are placed inside a folded paper containing 2,6-di-tert-butyl-4-nitrophenol (DTNP), wrapped in a plastic film that does not contain BHT (butyl hydroxytoluene) and are introduced in a oven for 16 hours 50 ° C. Phenolic yellowing was assessed visually or instrumentally using a spectrometer. The result is given on a scale of 1 to 5 (1 is poor and 5 is excellent).

Content of amino terminal groups

The content of amino terminal groups (AEG) was determined by a potentiometric titration method. The amount of 2 grams of polyamide is added to approximately 70 ml of 90% phenol. The mixture is kept under stirring and at a temperature of 40 ° C until complete dissolution of the polyamide. The solution is then titrated with 0.1 N HCl at approximately 25 ° C. The result is reported as equivalent / ton (eq / ton). In the case of analyzing fibers and articles, any residue or spinning finish must be previously removed.

Viscosity in solution (IVN)

The solution viscosity (IVN) is determined according to ISO 307. The polyamide is dissolved in 90% formic acid at 25 ° C at a concentration of 0.005 g / ml, and its flow time is measured . The result is reported as ml / g.

Example 1

A solution containing 28 kg of demineralized water and 10 kg of the AlSNa is added to 1250 kg of polyamide during step a1. of the polymerization, and an optical brightener additive is continuously added in the form of a liquid standard batch to the top of the rotating grid head, through a pump. AlSNA is introduced into the autoclave at the beginning of polymerization. The resulting yellowing-proof PA 66 granule contains 0.8% by weight of the reagent, AEG 30.7 eq / t and IVN 110.5. A multi-filament thread of PA 66 is produced that is yellow-proof with said granules of PA 66 that is yellow-proof and 0.4% by weight of an optical brightener additive, during extrusion by melt spinning.

The multi-filament thread of PA 66 yellow-proof is additionally textured at a linear density of 2x78 dtex and is woven to form a fabric.

Yellowish-proof PA 66 knitting showed good antiphenolic yellowing properties.

Example 2

A liquid standard batch containing 29.4% by weight of the AlSNa, 58.9% by weight of demineralized water and 11.7% by weight of an optical brightener additive is continuously added to step b0. at the top of the rotary grid head, through a liquid pump, at a melt spinning temperature of approximately 290 ° C. The resulting multifilament PA 66 yellowish-proof contains 1.0% by weight of the AlSNa reagent, 0.4% by weight of optical brightener additive, AEG 35.6 eq / t and IVN 107.2. The multi-filament thread of PA 66 yellow-proof is additionally textured in a linear density of 2x78 dtex and is woven to form a fabric.

Yellowish-proof PA 66 knitting showed good antiphenolic yellowing properties.

Example 3

A liquid standard batch containing 38.5% by weight of the AlSNa, 51.2% by weight of demineralized water and 10.3% by weight of an optical brightener additive is continuously added to step b0. at the top of the rotary grid head, through a liquid pump, at a melt spinning temperature of approximately 290 ° C. The resulting multifilament PA 66 yellow-proof contains 1.5% by weight of the AlSNa reagent, 0.4% by weight of optical brightener additive, AEG 36.9 eq / t and IVN 103.7. The multi-filament thread of PA 66 yellow-proof is additionally textured in a linear density of 2x78 dtex and is woven to form a fabric.

Yellowish-proof PA 66 knitting showed good antiphenolic yellowing properties.

Example 4

A yellowing-proof polyamide granule is produced according to Example 1. An additional 0.5% by weight amount of AlSNa is added to the extrusion stage as follows: a solid standard batch containing 20% by weight of AlSNa and 80% by weight polyamide 6.6 is combined with another solid standard batch containing 10% by weight of an optical brightener additive. The solid standard batch is produced previously by mixing the support, which is polyamide 6.6, with the AlSNa using a mixing extrusion process. The standard batch produced is continuously added to step b0. of the single-screw extruder in granular form, through a feeding apparatus, at a melt spinning temperature of about 270 ° C.

The resulting multi-filament PA 66 multi-filament contains 1.3% by weight of AISNa, 0.4% by weight of optical brightener additive, AEG 33.19 eq / t and IVN 98.04. The multi-filament thread of PA 66 yellow-proof is additionally textured in a linear density of 2x78 dtex and is woven to form a fabric. Yellowish-proof PA 66 knitting showed very good antiphenolic yellowing properties.

Example 5 - Comparative

A liquid standard batch containing 17.2% by weight of adipic acid, 69.0% by weight of demineralized water and 13.8% by weight of an optical brightener additive is continuously added to step b0., At the top of the rotating grid head, through a liquid pump, at the melt spinning temperature of approximately 290 ° C. The resulting yellowish-proof PA 66 multifilament contains 0.5% by weight of adipic acid, 0.4% by weight of optical brightener additive, AEG 29.3 eq / t and IVN 100.7. The multi-filament thread of PA 66 yellow-proof is additionally textured in a linear density of 2x78 dtex and is woven to form a fabric. Yellowish-proof PA 66 knitting showed good anti-phenolic yellowing properties.

Example 6 - Comparative

A liquid standard batch containing 23.8% by weight of adipic acid, 63.5% by weight of demineralized water and 12.7% by weight of an optical brightener additive is continuously added to step b0., At the top of the rotating grid head, through a liquid pump, at the melt spinning temperature of approximately 290 ° C. The resulting yellowish-proof PA 66 multifilament contains 0.75% by weight of adipic acid, 0.4% by weight of optical brightener additive, AEG 8.2 eq / t and IVN 74.5. The winding of the PA 66 multi-filament thread was not possible due to the low viscosity and very poor processability; therefore it could not be evaluated.

Example 7

A conventional PA 66 multifilament yarn, without any previous sulfonated reagent, but with optical brightening, became a textured PA 66 multifilament of 2x78 dtex, by a texturing process. A special cone oil was applied to the thread during step c4. The cone oil consists of a mixture of sulfonated reagent (Stabilon® CT), oils and surfactants. More specifically, the sulfonated reagent represents 18% by weight, the oil 71.4% by weight and the surfactant 10.6% by weight of the cone oil formulation. The oil for cones is applied to the thread using a metering pump and rollers.

The resulting yellowish-proof PA 66 multifilament contains 1.0% by weight of sulfonated reagent, 0.4% by weight of optical brightener additive ,? eq / t e IVN? The multifilament thread of PA 66 yellow-proof is additionally woven to form a fabric.

Yellowish-proof PA 66 knitting showed very good antiphenolic yellowing properties.

Example 8

A PA 66 multifilament yarn, produced in stage a according to Example 1 above, with 0.9% AISNa, and optical brightening, became a textured PA 66 multifilament of 2x78 dtex, with the use of a texturing process A special cone oil was applied to the wire according to example 7 above during step c4. The amount of Stabilon® CT applied during step c4 is 1.0%.

The resulting yellowish-proof PA 66 multifilament contains a total of 1.9% by weight of anti-yellowing additives, 0.4% by weight of optical brightener additive, AEG? eq / t e IVN? The multifilament thread of PA 66 yellow-proof is additionally woven to form a fabric.

Yellowish-proof PA 66 knitting showed excellent antiphenolic yellowing properties.

Example 9 - Control

A conventional textured PA 66 multifilament yarn of 2x78 dtex linear density was produced with the same characteristics as the above-mentioned threads, but without the reagent (but with 0.4% by weight of optical brightener additive). The results of the knitted fabric produced from them are AEG 36.8 eq / t, IVN 124.0.

Evaluation of the Examples:

As described above, each of the examples (Examples 1, 2, 3, 4, 5, 6, 7, 8 and 9) are evaluated to determine phenolic yellowing, the content of amino terminal groups (AEG) and the solution viscosity (IVN). The results of each of these examples tested are shown in Table 1 below.

TABLE 1

The results of the phenolic yellowing tests show that Examples 3, 4, 7 and 8 achieved the best property of the yellowing test. For example, example 8 obtained grade "5.0" and example 4 obtained grade "4.0", while comparative examples obtained lower grades (comparative example 7 (1.0)) or cannot be measured (comparative example 6) .

From the examples, it is possible to conclude that when AlSNa is added during the polymerization step (Examples 1 and 4), the polyamide article achieves a good yellowing test effect with a lower AlSNa content. For example, example 1 (0.8% by weight) showed a better yellowing test effect than example 2 (1.0% by weight); and example 4 (1.3% by weight) showed a better yellowing test effect than example 3 (1.5% by weight). The best result is achieved by combining the polymerization stage with the texturing stage. During the texturing stage, the sulfonated reagent is applied topically, which significantly improves protection against yellowing and maintains physical and mechanical properties.

With respect to processability and viscosity, Example 1 showed the highest IVN (110.5), which means that intrinsic viscosity and processability were less affected than the other examples, in particular comparative examples 5 and 6 , in which the processability was impaired due to the lower IVN, respectively 100.7 and 74.5. Example 4 and comparative example 5 showed very close viscosities, however, the processability of example 4 was better than comparative example 5. A sharp reduction in IVN is detrimental to the melt spinning process and the mechanical properties of the wire, for example, comparative example 6 showed poor processing conditions due to the very low IVN (74.5), which means that it was not possible to spin and wind the polyamide in coils, since the fiber did not meet the mechanical requirements minima.

In summary, when sulfonated reagents are introduced in an amount of 1.3, 1.5 and 1.9% by weight, it is possible to obtain very good yellowing test results with a very good processability. At 1.0 and 0.8% by weight with AlSNa, it is still possible to obtain good yellowing test results without processability problems. Therefore, the salts of AlSNa and aryl alkyl sulfonic acid are less detrimental to the process and viscosity than carboxylic acid (e.g., adipic acid) than comparative examples 5 and 6, and also show a Better yellowing test effect.

Claims (16)

1. Use of a sulfonated reagent in a process for producing a white polyamide article, comprising at least the following steps: to. polymerization of at least one monomer to obtain a polyamide in the form of a melt, granule or powder, b. formation of the polyamide article from the melt polyamide, granule or powder, c. optionally, conversion of the polyamide article using a texturing process, the sulfonated reagent is introduced during step a. and / or stage b. and / or step c., in order to provide resistance to phenolic yellowing to the white polyamide article obtained when in contact with plastic packaging material containing phenolic compounds. 2. Use according to claim 1, wherein the polyamide is selected from the group consisting of aliphatic, semi-aromatic, aromatic polyamides and mixtures thereof. 3. Use according to claim 1 or 2, wherein the polyamide is an aliphatic polyamide selected from the group consisting of polyamide 6, polyamide 6.6, polyamide 5.6, polyamide 5.10, polyamide 6.12, polyamide 11, polyamide 12, polyamide 10.10, polyamide 4.6 and mixtures thereof. 4. Use according to any of claims 1 to 3, wherein the polyamide is selected from the group consisting of polyamide 6.6, polyamide 6 and mixtures thereof. 5. Use according to any one of claims 1 to 4, wherein the sulfonated reagent is selected from the group consisting of sulfonated aromatic, aliphatic or alicyclic compounds. 6. Use according to any one of claims 1 to 5, wherein the sulfonated reagent is selected from the group consisting of sulfoisophthalic acids, sulfobenzoic acids, sulfosalicylic acid, sulfonic acids, salts thereof, anhydrides thereof and mixtures thereof. 7. Use according to any one of claims 1 to 6, wherein the sulfonated reagent is an alkali metal salt of sulfoisophthalic acid or an aryl alkyl sulfonic acid salt. 8. Use according to any one of claims 1 to 7, wherein the sulfonated reagent is the sodium salt of 5-sulfoisophthalic acid or the lithium salt of 5-sulfoisophthalic acid or mixtures thereof. 9. Use according to any one of claims 1 to 8, wherein the sulfonated reagent is introduced in an amount of 0.01 to 5.0%, preferably 0.3 to 2.0% by weight of the total weight of the polyamide article. 10. Use according to any one of the preceding claims, wherein step c. and the sulfonated reagent is introduced both during step a. as stage c. 11. Use according to any one of claims 1 to 10, wherein the polyamide article is a fiber, a thread or a filament, a deletion or a textile article made of a fiber, thread or filament. 12. Use according to any one of claims 1 to 11, wherein the phenolic compound is butylated hydroxytoluene (BHT). 13. Method for providing resistance to phenolic yellowing in white polyamide articles in contact with plastic packaging material containing at least one phenolic compound, comprising at least the following steps: to. polymerization of at least one monomer to obtain a polyamide in the form of a melt, granule or powder, b. formation of the polyamide article from the melt, granule or polyamide powder, c. optionally, conversion of the polyamide article using the texturing process, in which step c. and a sulfonated reagent is introduced both during step a. as stage c. 14. A method according to claim 13, wherein the sulfonated reagent is the sodium salt of 5-sulfoisophthalic acid or the lithium salt of 5-sulfoisophthalic acid or mixtures thereof. 15. A method according to claim 13 or 14, wherein the sulfonated reagent is introduced in an amount of 0.01 to 5.0%, preferably 0.3 to 2.0% by weight of the total weight of the article of polyamide. 16. An article of white polyamide resistant to phenolic yellowing, obtained from the method according to any one of claims 13 to 15.